Program Module #5: Photolithography

Program Module #5: Photolithography (Day 1 of 2)

[Note that the quizzes provided are named based on the material they cover, and NOT on the day that they are given.  I.e. The quiz labeled “Quiz – Electronics (day 1)” is the quiz that asks about the material covered on day 1 of the electronics module, and is meant to be given on day 2 of the electronics module.] 

Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 

Materials List:

1.)    Play-doh (1 “party pack” canister per student)

2.)    Objects with features of various scales (Chains, coins, small instrument components, etc.)

3.)    Brown paper (grocery bags)

4.)    Dixie cups

5.)    Vegetable Oil

6.)     Small paint brushes

7.)    Diffraction gratings

8.)    PDMS molds of diffraction gratings

                See http://education.mrsec.wisc.edu/293.htm for instructions in making molds.

9.)    Laser pointers

 

Pre-Class Preparations:

1.)    Copies of All Handouts, quizzes

Lesson Plan:

Objective:

  1. Introduce students to the concept of transistors and give them an appreciation for how close these objects can be in a computer.
  2. Introduce students to the processes of lithography as it relates to placing many items on a computer

         chip.

3.)    Performs hands-on activities related to the one types of lithography—imprint lithography. 

 

Agenda:

1.)    Big picture talk (5 min)

2.)    Administer quiz (10 min)

3.)    Lecture – Lithography, molds, imprinting (15 min)

4.)    Activity – Soft lithography (20 min)

5.)    Discussion of results (15 min)

6.)    Activity – Diffraction gratings  (25 min)

 

Additional Information for the agenda items:

1.)   In groups of two or three, students will examine the effects of imprinting different objects into a piece of flattened Play-doh.  The items to be used can be anything that makes a sufficiently interesting and detailed pattern.  In general, it’s good to have objects of varying size and complexity, such that the students can make molds that show all the features of the original object, as well as molds that fail to capture the smaller features.  Students will be asked to imprint the objects into the Play-doh and examine the resolution and the ability to make a distinct “replicate” of the item in the Play-doh.  Students should be directed to learn about the difficulties encountered when pressing down too hard, imprinting in general, and the fact that the imprint is the reverse of the original copy.

2.)    Students will examine diffraction gratings, and the patterns made by shining a laser through the grating.  The students may have already seen diffraction at work, depending on the order of the modules, but the concept is difficult enough that a second round of lecture and lab activity will likely be useful anyways.  Students will also examine PDMS molds taken of the same diffraction gratings, demonstrating that soft lithography done well can still be useful in capturing small features of the original objects.

 

Handouts and presentations:

  1. Notebook pages - Photolithography (day 1)
  2. Presentation - Photolithography (day 1)
  3. Quiz - Photolithography (day 1)

Program Module #5: Photolithography (Day 2 of 2)

 Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 

Materials List:

1.)    Following procedure in Berkowski et al, J Chem Ed, 82, 1365, 2005.

  • Handheld 365 nm UV lamp, one per 3-4 students
  • Prepared photoresist solution, one container per 3-4 students
    • Isobornyl acrylate (monomer)
    • Bis GMA (crosslinker)
    • 2,2-Dimethoxy-2-phenylacetophenone (photoinitiator)
    • Oil Red (dye)
    • For ~16 students, prepare using 10g of Isobornyl acrylate
  • Aluminum foil to wrap photoresist vials and containers to avoid light exposure.
  • Ethanol in squirt bottle
  • Wash container
  • Microscope slides, 2 per student
  • Coverslips, No 1 thickness, 2 per student
  • Masks – Patterns on transparency paper
  • Glass pipettes and bulbs
  • Gloves
  • Transparency sheets
  • Timer
  • Electrical tape (for taping together slides, covering edges)

 

Pre-Class Preparations:

  1. Make all necessary copies 
  2. Prepare photoresist solution.
  3. Print masks.

Lesson Plan:

Objective:

1.)    Students will be able to describe the process of photolithography and explain why it is an important step in developing a computer chip.

2.)    Students will perform an experiment that will demonstrate the process of photolithography through a hands-on process.

 

Agenda:

1.)    Big picture talk (5 min)

2.)    Administer quiz (10 min)

3.)    Lecture/Lab prep – Photolithography (20 min)

4.)    Activity – Photolithography (30 min)

 

Additional Information for the agenda items:

1.)    This is the last day of the module, and this module is traditionally last in the rotation.  As such, this is the last quiz the students receive.  A quiz covering the material presented on this day is available, but is not usually employed

2.) Photoresist solution must be prepared ahead of time and takes ~1hr to make. Solution is stable if it isn’t exposed to light, so can be prepared several days ahead of time if desired. Be sure all containers block light or are tightly wrapped in foil.

3.)    Masks will need to be prepared ahead of time for this activity.  Creative decision making as to the content of the masks is encouraged, and it is especially useful to make masks from entertaining, or at least recognizable, shapes.  Different ideas that have been suggested or employed include:  silhouettes of the students, student names or signatures, university mascots or logos, and Pokémon.

 

Note:  Depending on the class size, and the exact experimental details, this day can run a little short.  We traditionally have some small activity ready to fill in the last 15 minutes or so of the period if necessary.  In our most recent session for example, we included a short activity related to microfluidics produced from photolithography techniques..

 

Handouts and Presentations:

  1. Presentation - Photolithography (day 2)
  2. Quiz - Photolithography (day 2)